mike's garage, however, police found three rolls of duct tape which were sent to fiber expert donna wallace. >> i was able to rule out two of the rolls of duct tape, because it had visual differences from the tape on the bags. it was slightly different in color and it had indentations along the surface of the tape. >> but the third roll was another matter. unlike the regular tape, duct tape has a stronger. it takes more effort to rip a piece of duct tape from the roll, and the fibers leave a distinctive tear pattern at the end, which often is as unique as a fingerprint. >> it's called a fracture match exam, and it's a type of exam where you -- it's like a forensic puzzle. try to put the pieces back together to see if they were at one time a single piece. >> w wallace used a high-powere microscope to compare the end of the roll of tape found in garvin's garage to the ends of all the pieces found with shirley's body. and she discovered that the ripped end on the roll of duct tape lined up perfectly with the piece found with shirley's body. >> the fact that i was able to fracture match these t